Tile and stone floors are typically quite expensive for both materials and the labor required for their installation. Since replacement of an entire floor or even individual tiles or stones is relatively costly, standards for materials and installation methods are provided to the industry by The Tile Council of North America (TCNA). This organization references American National Standard Institute (ANSI) test standards, which in turn use American Society for Testing and Materials (ASTM) test methods.
Tile and stone floors are typically installed in areas prone to wetness, such as bathrooms, kitchens and laundry rooms, and often directly on an on-grade or below-grade concrete slab. Such slabs are often sources of moisture or moisture vapor that can be very detrimental to the flooring installation. More specifically, in many locations in the United States, concrete slabs for houses and other building are poured directly on the ground. With shifting soil and expansion and contraction of the ground during rainy and very dry periods, it is very common for foundation slabs to develop cracks. Unfortunately, in cases where tiles or stones are directly adhered to the concrete slab, the tiles, stone or other flooring, and/or the mortar placed therebetween, will also typically crack. Such cracking often results in requiring replacement of the floor or costly remedial work on portions of the flooring.
In order to avoid installation problems due to moisture and concrete cracks, Tile Council of North America recommends the use of specially designed membranes (underlayments), which must pass very stringent test requirements of ANSI A118-10 Load Bearing, Bonded, Waterproof Membranes for Thin-set Ceramic Tile and Dimension Stone Installation and ANSI A118.12 Crack Isolation Membranes for Thin-set Ceramic Tile and Dimension Stone Installation, respectively. Waterproof Membranes and Crack Isolation Membranes are separate entities, with some installations requiring the use of both types.